Path to toolchain file supplied to cmake(1).

This variable is specified on the command line when cross-compiling with CMake. It is the path to a file which is read early in the CMake run and which specifies locations for compilers and toolchain utilities, and other target platform and compiler related information.

Relative paths are allowed and are interpreted first as relative to the build directory, and if not found, relative to the source directory.

This is initialized by the CMAKE_TOOLCHAIN_FILE environment variable if it is set when a new build tree is first created.